[Music] [Music] Hello everyone. Hope you're all doing good. In this video, I want to discuss with you about the mechanism of labor. First, let us see what is labor. Labor is a process in which the fetus especially after the period of viability is going to expel from the uterus through the genital tract to the exterior world. Clear? So fetus expul from the uterine cavity through the genital tract to the exterior world. And all these things should happen after the period of viability. Now what does WH says about labor? See who has given a definition for labor. I'm going to share you the keywords alone that will help you in knowing what is a normal labor means. Okay. So if you take a normal labor, it should have the following features. Number one, it should be spontaneous in onset. Then the labor should remain low risk from the starting of the labor throughout the labor as well as after delivery also. Then the infant should be mostly in a vertex position. Any position other than vertex is considered a small position and it should be spontaneously born and a normal labor should happen between 37 to 42 weeks of gestational age. And the birth should happen through the vaginal root. And after birth also the mother and baby should be in a good condition. Clear? So all these points should be tick marked to say that it is a normal labor. Clear? Once again I'll come up. So WH definition for normal labor. First one it should be spontaneous and onset. Then there should be low risk from the starting of the labor throughout the labor and the delivery also should be low risk. Then the infant should be in vertex position and it should be spontaneously born. It should happen between 37 to 42 weeks of gestational age. Then it should happen through the vaginal root and the mother and the baby should be in a good condition even after delivery. Clear? Right. Now we have to know some important points. Okay, we have three Ps of labor. Okay, so these three Ps are very important. Okay, so these include number one the passage, number two the passenger and number three the powers. Okay, now we'll see what are these individually. First one is about the passage. So passage means it includes the bony pelvis and soft tissues. So bony pelvis can be assessed by clinical pelimetry and soft tissues include your lower uterine segment formation then cervical dilation and then also the vagina which is going to distend and stretch. Clear right now we'll see about the passenger that is the fetus. Okay. So how the features of a fetus should be to go through a normal labor. The lie of the fetus should be longitudinal. The position favorable and the most common position is left oipto anterior. Presentation as we have seen already in the WH definition it should be a vertex presentation and attitude of the baby which is favorable is a universal flexion. Okay. The head of the fetus should be at a station zero and below and fetal weight should anywhere between 2 to 3.5 kilogram. Okay. Now let's start with the mechanism of labor. I'm going to discuss with you about the mechanism of lift oipto anterior position which is the most common position. Okay. So, so now I'm going to discuss about the mechanism of labor in detail and I'm going to discuss about left oto anterior position. Okay. So, mechanism of left oipital anterior position. Here you have to know that this is the common longitudinal capalic presentation. Attitude of the fetus is flexion. Presenting part is the posterior part of the vertex. posterior fontel and the denominator is going to be the oiput. Clear? Now we'll see what are the cardinal moments of labor. Cordinal movements of labor. See this can be remembered by using a pneumonic. I generally remember as it was a fireer. Okay. So number one moment is going to be engagement. Number two is descent. Number three that is F is going to be flexion. Number four IIR is going to be internal rotation. Then again E is going to be extension and R is going to be resty tution. Okay. And after that add one more year. So this will become external rotation and sometimes you can even add a eighth one that is expulsion. Okay. So it was a fire error. Okay. So this how you can remember the corner movements of labor. Okay. So the order is going to be the uh same. So no changing in order. And remember to join this IR then you will remember about what is the and what is uh this R. Okay. And this ER will go together. Here IR will go together and here ER will go together. Clear? Yes. Now we'll see about engagement. So when we speak about engagement in simple words engagement means dipping that is the fetal head is going to pass through the inlet. Okay. So it is dipping when the presenting part of the fetus has passed through the plane of inlet. In other words, if I explain even more precisely, I'm going to say that the widest diameter of the fetal head is going to pass through the inlet. Okay? Suppose if it is a capalic presentation, it is the biparital diameter which is going to be the presenting diameter that is passed to the inlet. Suppose if it is a bridge presentation, it is going to be the inter troantric diameter. Clear? Okay. And remember another fact that engagement in primary gravidas happen two to 3 weeks before term. Whereas engagements in multigraidas will occur usually after the onset of labor. So engagement can be assessed by doing either uh abdominal or vaginal examination. Suppose while doing examination uh through the parabdomen examination repeating. So assessment of the engagement can be done through a perabdomen or a pervaginal examination. While doing a perabomen examination suppose if engagement has not occurred then it is said to be have a floating head. Okay. In per vaginal examination, the bony presenting part in pervaginal examination the presenting part should be at the level of fial spines or it should have crossed the spines. Clear? So presenting part should be at or nearly at the level of isial spines and remember this presenting part should be the fetal skull bone. Okay. Sometimes if cases of caput we'll be seeing a soft swelling. So caput uh presentation is not considered to be the engagement. Okay. Yes. Now remember that the fetal head engages with its sagetal suture that is the antroposterior diameter of the fetal skull in the transverse diameter. of the maternal pelvis. Clear? Okay. Now we'll discuss about some of the important and confusing terms centilism and asynism. See it is cintilism. Okay. Silism means the S4S you have to take. Okay. So we are going to talk about the sagittal suture alone. So the sagittital suture is going to be in the midway between the pubic symphysis and the sacral promonry. Okay. So if I draw the pelvis like this. Okay. If I'm going to draw the pelvis like this, say this is the sacral promonry. Okay. And here we are having the pubic symphysis. Okay. And if I take the fetal head like this, I'm going to check for the sagittal suture position. So this should be in a midway like this. Sorry. This should be in a midway like this. Okay. So this is centralism. But if for any reasons this position is not maintained the sagittal switchure is going to go towards the pubic symphysis or towards the sagal promonary then it will be named accordingly and that condition is collectively called as centilism. We'll see the types now. Okay. In a centilism you have two types. Okay. You have the anterior asentilism and the posterior asalism. Okay. So anterior asentilism is when the anterior parietital bone is going to present. Okay. So here anterior parietital bone presence whereas in posterior asentilism your posterior parietital bone presence. Okay. Now we'll see about the different types of asententralism. So asentism can be anterior asism or posterior asism. Okay. So anterior asentism is where the anterior parietital bone is going to be at a lower position than the posterior parietal bone. Okay. Whereas in posterior asism the posterior parietal bone is going to be the presenting parietal bone or the parietal bone at lower position. Okay. And if you see in anterior asism the sagittital suture will be closer to the sacral promonry. Okay. Don't ever get confused here. Okay. So sagittal suture is close to the sacral promonry. Whereas in posterior asentilism, sagittal suture is close to the pubic symphysis and anterior asentilism is also known as needlessly oblig. Okay. Whereas posterior asentism is also known as litzman oblquity. Anterior asentism is more common in multiparis whereas posterior asentism is more common in nulliparas. Okay. So how I am going to remember is see anterior asentism it is also known as nigles obligity it is more common in multiparas and you remember this yes okay so this yes is going to take sacral promoter it is an&m okay so axillary nurse midwife okay so that abbreviation I I have kept as a&M. So it is anterior obligity that is anterior raisinism obligity common multipara and this is sacral promonry. Okay. If you want you can add a p also. Okay. So we'll see the picture for better understanding now. So this is a normal centralism. Okay. But if you see the sagittital suture. Okay. So this is the sagittital suture like. So it is midway between the pubic symphysis as well as the sacral promonry. Okay. Whereas if you see the anterior asynism which is the nucleus oblity this uh sagittal suture is going backwards. Okay. And it is going to towards the sacral promonry. Okay. So that one you have to keep it in mind. It is going backwards. Whereas in the posterior asentism or the litzman obligative what is going to happen? The sagittal suture is coming forwards. So when this is happening the parietital bone which is going to present is for the anterior asynism it is the anterior parietal bone which is going to present and posterior asynism it is the posterior parietal bone which is going to present. Clear? So the parietital bone name goes synonymous with this type of asynism and the sacral promonry uh sorry and the sagittal suture movement goes towards the opposite of the name of the asynism. Okay. Right. Why this is important? Cintism or asynism. Why it is important? See, when the baby is in centralism, the presenting diameter is going to be biparital diameter which is around 9.5 cm. Whereas in asynchronism the presenting diameter is going to be supra separatital diameter that is around 8.75 cm. Okay. So when this is happening sometimes asence there is a reduction in the presenting diameter. This will be favoring favoring a larger hit to pass through the inlet. Yes. Right. Suppose if you are able to find a marked or persistent asynism then that time asism becomes abnormal. We'll see the next cordinal moment about descent of the fetus. So descent see descent is one of the cordinal movement in labor which is going to start right from the engagement and it is going to happen along with the other cordinal movements also. Okay. So whatever cordinal movement comes okay internal rotation with the descent flexion with the descent extension with the descent external rotation with the descent descent is going to happen continuously. Okay. So it continues throughout the labor and other movements are going to be superimposed. Regarding descent, sometimes the primary gravida descent may not occur even until the second stage. So remember in descent for primary gravida it may not occur till her second stage whereas for the multigraida the descent will usually start with the engagement itself. Okay. So what I told for engagement primy the engagement occurs first. Okay. And for the multi it will be occurring with the onset of uterine contractions. Right. Whereas for the descent it will be occurring early for the multigravida. Whereas for the primary gravida it will not occur till the second stage. Clear? Yes. And we'll see what are the factors that is going to cause this descent. Okay. Factors of forces causing descent. Number one, it is the direct pressure given by the uterine contractions. Number two, the pressure given by amniotic fluid. Number three, the bearing down efforts given by mother. And here the maternal abdominal muscles play an important role. And the fourth factor is the fetus. Okay. So there is extension and straightening of the fetal body. Clear? So all these factors put together will be helping in the descent of the fetus. Okay? And remember another point what I told you descent is going to happen right from the engagement till the birth of the baby. Okay? It will be occurring with all the other cardinal moments also. Clear? Yes. Now the next cornal movement is flexion. Okay. See flexion is the natural attitude of the baby. So in nidro itself it is the baby is going to be in the universal flexion. Right? But as the cordinal moments of labor are started and when it is going to descend down and it is going to meet a resistance the resistance can be from the cervix the pelvic floor or the pelvic side walls. What happens is this is see imagine this is the cervix or pelvic floor or pelvic wall. The baby is going to descend descent descend like this. Already it is in a flexion and when it is going to hit it is going for a further flexion like this. Clear? So what I say to you is it exits before the onset of labor. This is the natural attitude of the fetus in neutral. But as the descending head meets the resistance, the resistance can be from cervix or pelvic floor or pelvic side walls. then it under goes further flexion. Clear? And here you have to remember another point that as the baby is getting flexed. Okay, consider this is the anterior part and this is the posterior part of the fetal head. Okay. So as it is going to get flexed, okay, we will be getting okay the oiput down. Okay, the oiput is going to come down whereas uh the anterior part of the head. Okay, it is going to go inside like this. Okay, so finally oiput will be the leading thing and when you do a pervaginal examination you'll be able to palpate the posterior fontel. Okay, so the oiput will be ahead of the sinciput and the posterior fontinal will be ahead of the anterior fontel. Clear? And it will be like the baby's uh chin will be going and touching its chest. Clear? Okay. So what happens is oiput descends in advance of the sinciput then posterior fontel is lower than the bregma and the posterior fontel is lower than the brema. Also, when this is happening, the baby's chin is going to touch his or her chest. So remember another important point that while this flexion is going on the presenting diameter is also going to change. Okay. Suppose if you say that it is in the oipital frontal diameter which is around 11 cm while this extra flexion is happening. This will change to subosip fragmatic diameter which is 9.5 cm. Okay. See it may seem like only there is a reduction of 1.5 cm but even this reduction of 1.5 cm during a natural labor to for the fetal head to pass through the pelvis is very very important. Clear? So this is the importance of flexion. Now we'll pass on to the next one. Internal rotation. So in internal rotation I want you to understand two factors. Number one, if you take the maternal pelvis, the inlet is going to be transversely oval. Whereas the outlet is going to be anteriorly wal. Right? And if you take the fetal head, how it is going to engage in the maternal pelvis in the inlet? This is going to engage in the oblique diameter or anterior diameter. Antroposterior diameter. Yes, mostly. And in the outlet it will be coming to the androposterior diameter. Okay. So this is going to just match with the pelvic diameters. Clear? So what is going to happen is the oiput is going to rotate now. Okay. So the oiput is going to rotate how many degrees means exactly 45° to the right. Okay, that is it is going to rotate from the occipital anterior position towards the right 45°. So what will happen if it is in the left oipto transverse position? It is going to come to the left oipto anterior position. Okay, see I'll give you an example. So if you take this is the circle right we'll take here is the pubic symphysis and here is the sacral promonry okay and uh I'll be dividing the quadrants also so this is oipto anterior this is oipto posterior let's keep this as the left side and this is the right side so you have left oipto anterior left oipto transverse and left oipto posterior yes here also you Right occipital anterior, right occipital transverse and right oipto posterior. Okay. So 45° rotation means what is going to happen is if it is in the left oipital transverse position, it is going to come to the left oipto anterior position. Yes. And also suppose if it is in the left oipto anterior position, it is going to come exactly into the oip anterior position and so on. Clear? So I hope you'd have understood this and uh sometimes okay sometimes what is going to happen is rarely in some cases posterior rotation may happen and it can present as oto posterior position also. Clear whatever oto posterior right oto posterior left oipto posterior so it can present to oipto posterior position also. Clear? Yes. So what is going to happen is in twothird of the cases most of the time internal rotation will be completed before it reaches the pelvic floor. Okay, before it reaches the pelvic floor whereas in 1/4 cases it will happen only after the fetal head reached the pelvic floor. Clear? Yes. Now you have to understand the fact that uh we have seen about the fetal head only. So the fetal head is going to transform to the occipto anterior position. Right? But what about the shoulders? The shoulders are still in the oipto anterior position left oipto anterior position. Right? So there is a difference between the fetal head and the fetal shoulders. Here 45° is not uh changed by the shoulders. Okay? So what happens is there is a neck flexion here. Okay. The neck is in a change of flexion. Okay. The neck is twisted around 45°. Now clear. So this uh you have to understand this factor also. Okay. So that is a neck twisting around 45°. And uh most of this internal rotation will be happening during the second stage of labor. Clear? Right. So if you take the head is in the androposterior diameter then the shoulders are left behind in the left oblique diameter. So there is a twist in the neck around 45° and most of these uh uh events are going to happen during the second stage of labor. Clear? Okay. We'll see the next cornal moment that is extension. See when the fetus is going to come and reach the pelvic floor two factors are going to come into play. Okay. So what are the two factors? First factor is the uterus which is going to give downward pressure and number two is pelvic floor which is going to give resistance. Clear and also understand the fact that the anterior wall is going to be formed by the pubis which is 4 to 5 cm. Okay, roughly and which part of the fetal head is going to be in contact with the anterior wall? Yes, it is the oiput. Okay, so this is the oiput is contact here. Right. And same way the posterior wall of the pelvis is formed by the sacum. And this is going to be around 10 to 15 cm. And here ciput of the fetal head is going to be in contact with the posterior wall. Clear? Right. The point you have to understand here is the sinciput is going to travel a longer distance than the oiput. Okay. And also there is bulging of the pyreneium. Okay, bulging of the pennium that is followed by crowning. Okay, that will happen with the further descent. Okay. So with crowning what is going to happen is oiput hitches under the pubic symphysis and it doesn't recede. Okay. So that is exactly what is crowning. Clear? So after crowning what happens is first the oiput is going to pass down. Okay. Then there is a rapid extension of the body that is going to cause uh the fetal uh face to born in an order. Okay. So uh you can imagine your face itself. Okay. It starts right from the brema then forehead will be born then nose will be born. Then your mouth and then finally your chin. Clear? And immediately after delivery what happens is the fetal face will be lying as such it is going to touch the maternal anus. Clear? So first one is oiput passes the outlet slowly. There is rapid extension of the body of the fetus. So that will cause the cinciput to sweep across the sacrum. Okay. Sinciput sweeps. So that causes the sinciput to sweep across the sacrum and the baby is born in the order. First comes the brema, next comes your forehead, next comes your nose, mouth and chin. And after everything is out the chin will be lying such that it will be touching the maternal anus. Clear? Right. And the next coordinate movement is external rotation. In external rotation I have to explain about three factors. I have to tell about restitution first. Okay. So if you ask me what is restitution already I said to you there is a neck twisting which is existing. So the twisting hasn't recovered till the delivery of the fetal head. Okay. So after the head delivery what happens is the shoulder is not going to make any change. Understand that point. Okay. The head is going back to the original position. Okay. So I told you the head is in the oip anterior position now. Right. So the head is in the oip anterior position. Now again it will go back to its original position which is left of oip anterior position. So as it is doing uh as this twisting is undone what happens the head and the shoulders are going to be in the same alignment. Clear? Right. So that is what is about restitution. You have to know about shoulder position now. So the diameter of shoulder which is going to present is this acromial diameter. Okay. And remember this bisacchromial diameter is going to present in the antroposterior diameter of the pelvis. Accept it. So the anterior shoulder is under pubic symphysis and the posterior shoulder is under the sacral chrom. Okay. Now the first shoulder that is going to be born is the posterior shoulder by a lateral flexion mechanism. Okay. So there is late reflection. Imagine this is the anterior shoulder. This is the posterior shoulder. Okay. So there is a late reflection mechanism which is going to deliver this posterior shoulder followed. And as the posterior shoulder is delivered the anterior shoulder follows. Clear? And then we have to see about expulsion. Expulsion means once the head is delivered and shoulders are delivered the rest of the baby is going to come out easily. clear and it needs only uterine contractions. So far we have traveled with the baby only in imagination. Now we are going to see this uh picture for better understanding. Right? So this is the picture. See first there is engagement, descent and flexion. They have shown it in a single diagram. Okay. So there is engagement, descent and the baby is in a universal flexion position. Right? And the next one is what is going to happen is this is in the left oipital anterior position. Okay. See when you are seeing such kind of diagrams what you have to know is your right is patient's left and your left is patient's right because you'll be seeing the patient. You have to imagine as if you're seeing the patient then it will be easy. Okay. So this is going to be the patient's left side and this is going to be the patient's right side. Clear? And then you have to check where is the sacrum and where is the pubic symphysis. Okay. So here the sacrum is here. Okay. So this is the sacrum and this is the pubic symphysis. Okay. So this is the right side. Okay. In this picture they have shown the and in the fetal head you have to find the oiput. Okay. So to find the oiput what you have to do is you have to check for the anterior fontinal. Okay. So this is the anterior fontinal. Right. So here is the posterior fonten. So that means this is going to be the oiput clear. So this is a left. Okay. Oipto and it is anterior because the oiput is towards the pubic symphis. So it is a left oipto anterior position. That's it. Clear? Okay. Now the baby's in the left oipital transverse position. Then what is going to happen is there is a state of internal rotation. Okay. And when this internal rotation is happening see the oiput is turning towards the front now. Okay. The oiput has turned towards the front. Then there is external uh rotation that is restitution has happened that is untwisting has happened. Then there is extension where the rotation is complete. Then the shoulder rotation is going to happen. Okay. The shoulder rotation has happened and then the extension is complete and finally the expulsion has occurred. Clear? Okay. So in this picture if you see in this figure they have shown engagement isn't and flexion together. Okay. Here they shown the position of the fetal head. You have to understand while doing this kind of picture you have to understand that the patient's left is towards your right and the patient's right is towards your left. Clear? So this is my right. So obviously the patient will be having a left side here and this is my left and the patient's right side will be here. Clear? Okay. You have to imagine as if you are seeing the patient and then you have to see the pelvis and you have to find where is the pubic symphysis and where is the sacral promonry. I suppose to think that when there is a small joining like this, it is going to be the yes pubic symphysis and this is going to be the sacrum. Clear? And also you have to check for the fetal head and where the oiput is present. Always remember when they have shown something in a diamond shaped what is it? It is the anterior fonten. So this is going to be the sensiput of the baby. So this is obviously going to be the oipital of the baby. And now join everything together. So it is the left oipto transverse position. So this is exactly like this. Right? So it is the left oipto transverse position. So after engagement isn't flexion it is going to be at firer. So IR is going to join now and it is yes internal rotation. So in internal rotation what has happened is from the transverse position this has changed into oipota anterior position right then comes your extension where the rotation is complete okay it has completely turned down so by the time internal rotation has completed okay by the time of extension then extension is totally complete here see the baby's head is coming out now and then what happens is there is external rotation there is a restitution is happening the twisting of the shoulders is not undone so that is being completed here Right? And then the shoulders are going to rotate. Okay? And finally what is going to happen is the rest of the fetus is going to be born without any trouble. That is called as expulsion. Clear? Right? Now after the expulsion of the baby, what else is left inside the uterus? Placenta is left. Right? So we'll see the birth of the placenta also. So birth of the placenta. Now after the expulsion of the fetus what is going to happen is the uterine contractions are going to start again after a few minutes. Okay with this uterine contraction whenever uterine contraction is happening what we know that the upper segment is going to contract right and only in the upper segment the placenta is attached so it is going to retract. Retract means the cells of the uterus are going to become smaller this time. Okay. So with this retraction what is going to happen is the placental bit is also going to become smaller. Okay. So the placental bed area is going to become smaller and the placental bed area is going to become smaller means the placenta is going to be separated from the disa along the spongy layer. Okay, then the separation will be happening. Can you understand? So now first point within few minutes the uterine contractions begin again. Then we know upper uterine segment under goes retraction. So the decreases placental area of attachment. So this leads to detachment of placenta along the spongy layer of desida. So placenta will be separated from the wall of the uterus then. Okay. So then it will be expelled down into the vagina and there will be bearing down a photo of the patient also helping this. clear and uh there are two methods of placental separation we have Duncan's method okay what happens in Duncan's method see the lower edge of placenta comes first lower edge of placenta comes first okay so as the lower edge of placenta is coming both the anterior surface of the placenta and the posterior surface surface of the placenta that is both the maternal surface of the placenta and fetal surface of the placenta are going to come together right. So maternal surface, maternal and fetal surface present together and then we have the sulc method here. What happens is remember the C. Okay, C means the placenta is going to separate from the center. Okay, C this P. Okay. So the placenta is going to separate from the center. Okay. So that means this is the maternal surface and this is the fetal surface. So in the suli method the fetal surface is going to present first. Clear? So this is the Duncan's method of placental separation where the antroposterial surface that is maternal and fetal surface are going to present together and it is going to happen from one edge. Whereas in Duncan's method remember C so from the center it is going to separate. So from the center it is separating means the fetal surface is going to present. Okay. So but we don't have any significance with these methods but you have to know just that there are two methods of placental separation. Clear? So with this we are completing this topic on mechanism of labor. We have discussed about all the coordinate moments of labor, the importance and also the birth of the placenta. So until we meet in the next video, take care, happy learning and bye-bye.